Stub shaft conveyor roller

ABSTRACT

A conveyor roller includes a generally cylindrical roller tube and a pair of stub shafts rotatably mounted in each end thereof. At least one of the stub shafts is mounted for axial movement between an extended position and a retracted position. When in the extended position, the stub shafts on each end of the conveyor engage respective mounting holes in the conveyor frame. To insert the conveyor roller in the conveyor frame, the movable stub shaft is moved to a retracted position while the roller is lowered into the conveyor frame. When the stub shaft aligns with the mounting holes in the conveyor frame, the stub shaft is urged back to the extended position by a biasing member to engage the mounting hole in the conveyor frame.

This application is a continuation of originally filed U.S. patentapplication Ser. No. 08/939,966 filed Sep. 29, 1997 and issued as U.S.Pat. No. 6,076,647.

FIELD OF THE INVENTION

The present invention relates generally to improvements in rollers forconveyors and, more particularly, to a conveyor roller of the type whichis mounted on stub shafts.

BACKGROUND OF THE INVENTION

Roller conveyors are commonly used in many industries to move packagesor materials. In general, a conveyor roller comprises a plurality ofindividual rollers mounted between two parallel frames. The rollertypically comprises a tube having a bearing in each end thereof which isrotatably journaled on a roller shaft that extends longitudinallythrough the tube. The roller shaft protrudes from each end of the rollertube and engages mounting holes in the frame.

Frequently, the roller shaft not only serves to mount the roller, butalso functions as a structural element of the conveyor frame. In suchcases, the ends of the shaft are drilled and tapped. Bolts extendingfrom the outside of the frame are threaded into the tapped holes in theroller shaft to secure the frame members and rollers together. Thisapproach to the construction of conveyors makes assembly of the conveyortime consuming and difficult. Moreover, this method of constructingconveyors makes it difficult to replace a single roller.

Another method to mount rollers in a conveyor frame is to use a rollerhaving a through-shaft which is spring-loaded. In this case, the framemembers are held together independently by a series of cross membersrather than through the rollers. The rollers generally are installedafter the frame is assembled. To install the roller, the shaft is movedaxially against the force of the spring and “snaps” into place when theshaft aligns with the mounting hole in the frame member. This methodmakes assembly of the conveyor much simpler and facilitates thereplacement of rollers when they become worn or defective.

Several attempts have been made in the past to eliminate through-shaftsin the roller. In place of a single thru-shaft, separate stub shaftshave been used to support opposing ends of the conveyor roller.Typically, these stub shafts are bolted to the conveyor frame before theframe is assembled. The conveyor roller is then inserted over the stubshaft as the frame is locked together to create a final assembly. Thismethod of mounting rollers in conveyors also makes assembly difficult.Moreover, this method essentially precludes prefabrication of theconveyor frame.

Accordingly, there is a need for a new method for mounting conveyorrollers in a frame which does not rely on a through-shaft extendingthrough the roller, allows prefabrication of the conveyor frame, andfacilitates ease of assembly.

SUMMARY AND OBJECTS OF THE IVENTION

The present invention combines the advantages of spring-loaded shafts,which make installation of the roller quick and easy, and a shaftlessdesign which eliminates the need for a longitudinal through-shaft. Toachieve these advantages, the present invention utilizes a sliding stubshaft which is spring-biased to an extended position. The stub shaft canbe pushed inward against the force of the spring to allow insertion ofthe roller into a prefabricated frame. When the stub shaft aligns withthe mounting holes in the frame, the spring pushes the stub shaftoutward to engage the mounting hole. One advantage of the presentinvention is that it enables quick and easy assembly of a conveyor. Theconveyor frame can be prefabricated at the factory while the rollers areinstalled on site. Further, the present invention allows for easyreplacement of a worn or defective roller without the need todisassemble an entire conveyor section.

The spring-biasing of the stub shaft also produces advantages not beforerealized in conveyors. The spring-biasing tends to center the rollerafter it is installed so that its rotating members do not rub againsteither frame member. The spring also allows shock absorption to takeplace when packages or other conveyed materials are moved laterallyacross the conveyor as they are loaded or unloaded. Furthermore, theconstant preload on the springs eliminates vibration and noise whichwould resonate through the conveyor frame structure.

Yet another advantage of the present invention is its reduced weight. Byeliminating a through-shaft that extends through the roller tube andreplacing it with two smaller stub shafts, the total weight of theconveyor roller is reduced. Since conveyors use many individual rollers,the total weight reduction in a conveyor can be substantial. This weightreduction makes the conveyors more portable in the event that theconveyors need to be moved from one place to another. Also, shippingcosts are reduced.

Yet another advantage which is beneficial in the food handling industry,is the ability to produce a relatively low cost, non-corrosive conveyorroller. In the food handling and chemical industries, conveyor rollersfrequently employ stainless steel through-shafts. Sometimes, theadditional cost of stainless steel makes the installation and use ofconveyor systems impractical from a cost standpoint. By eliminating thethrough-shaft in its entirety, the stub shaft can be supplied withsophisticated corrosion resistant materials. Because the parts are sosmall, it does not negatively impact the overall cost of the system.

Another feature of the conveyor roller is increased safety. Theretention of the roller in the frame is assured even in the event ofbolt failure or vibration which could cause the bolt to fall out. Ineither instance, the spring-loading bias on the stub shaft acts as areductive retention system to prevent the roller from falling out of theframe.

Other objects and advantages of the present invention will becomeapparent and obvious from a study of the following description and theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial cross section of the conveyor roller of the presentinvention showing the stub shaft in a normal extended position.

FIG. 2 is a cross section of the conveyor roller being inserted into aconveyor frame showing the stub shaft in a retracted position.

FIG. 3 is a cross section of the conveyor roller after its insertioninto the frame showing the stub shaft in a partially extended positionand engaged with the mounting holes in the frame member.

FIG. 4 is an end view of the second embodiment of the conveyor roller.

FIG. 5 is a partial cross section of the conveyor roller of the secondembodiment showing the stub shaft in a normal extended position.

FIG. 6 is a cross section of the conveyor roller of the secondembodiment being inserted into a conveyor frame showing the stub shaftin a retracted position.

FIG. 7 is a cross section of the conveyor roller of the secondembodiment after its insertion into the frame showing the stub shaft ina partially extended position and engaged with the mounting holes in theframe member.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, and particularly to FIG. 1, the conveyorroller of the present invention is shown therein an indicated generallyby the numeral 10. The roller 10 is adapted for use in conveyors,packaging machinery, linear motion material handling devices, andtreadmills, but may also have other applications. The roller 10 ismounted between parallel frame members 12 which support the roller 10 atopposite ends thereof. The frame members 12 form part of a conveyorframe and may be held together, for example, by cross members (notshown). Each frame member 12 has a series of mounting holes 14 formedtherein for mounting the roller 10. The present invention isparticularly related to an improved mounting system for mounting theroller 10 in the conveyor frame.

The roller 10 comprises a generally cylindrical roller tube 20 which isrotatably journaled on a pair of stub shafts 50. A bearing housing 22 isinserted into each end of the roller tube 20 and houses a bearing 38 inwhich the stub shaft 50 isjournaled. The bearing 38 is retained byfriction in the bearing housing 22. A bearing shield 40 fits on theouter end of the stub shaft 50. The stub shaft 50 and bearing shield 40are biased by a spring 60 to an extended position as shown in FIG. 1.The stub shaft 50 can be moved to a retracted position by applying aforce to the end of the stub shaft 50. With the stub shaft 50 in aretracted position, it is easy to insert the roller 10 into an alreadyassembled conveyor frame.

The bearing housing 22 is typically molded from a plastic material. Thebearing housing 22 includes an outer cylindrical wall 24 and an innercylindrical wall 26 which define an annular cavity 28 therebetween. Theouter wall 24 is sized to provide an interference fit with the rollertube 20. The inner wall 26 frictionally engages and holds the rollerbearing 38. The roller bearing 38 is pressed into the bearing housing 22until it engages the back wall 30. Back wall 30 of the bearing housing22 includes a center opening 31 through which the stub shaft 50 extends.

The outer end 32 of the bearing housing 22 includes a seal cavity 34which, in conjunction with the bearing shield 40, provides a labyrinthseal to prevent dirt and other contaminants from reaching the bearing38. A lip 36 is also formed at the outer end 32 of the end cap 22 whichbutts against the end of the roller tube 20, which is bent inwardslightly to help hold the bearing housing 22 in place. The inner end ofthe outer wall 24 is slightly tapered to facilitate insertion of the endcap 22 into the roller tube 20.

As previously mentioned, the bearing housing 22 houses a bearing 38. Thebearing 38 may preferably be a radial ball type bearing as shown in FIG.1. However, it should be understood that the present invention will workequally well with molded plastic or bronze bushing designs. The functionof the bearing 38 is to reduce friction as the roller tube 20 rotatesabout the stub shaft 50.

The stub shaft 50 includes an inner portion 52 and an outer portion 54.The inner portion 52 has a cylindrical configuration and is journaled inthe bearing 38. It should be noted, however, that the inner portion 52of the stub shaft 50 and the inner race of the bearing 34 could have apolygonal configuration without departing from the spirit of the presentinvention. The outer portion 54 of the stub shaft 50 preferably has ahexagonal configuration and is adapted to mate with a similarly shapedand sized opening 14 in the mounting frame 12.

A small flange 56 is formed at the inner end of the stub shaft 50. Thepurpose of the flange 56 is to act as a stop when the stub shaft 50reaches an extended position. The flange 56 is designed to butt againstthe bearing 38 to prevent the further extension of the stub shaft 50.

A threaded hole 58 is located through the center of the stub shaftformed at the end of the outer portion 54. The threaded hole 58 isadapted to receive a bolt 62 which extends from the outside of the frame12 into the threaded hole 58. The purpose of the bolt 62 is to securethe roller 10 in place after it has been inserted into the frame 12.

The bearing shield 40 is press fit onto the outer portion 54 of the stubshaft 50. The bearing shield 40 includes a hub 42 and a cover portion44. The hub 42 includes a hexagonal bore 45 which is sized to provide atight, frictional fit with the outer portion 54 of the stub shaft 50.The cover portion 44 extends radially outward from the hub 42 to providea cover for the bearing 34. Two cylindrical walls 46 and 48 projectinwardly from the back side of the cover portion 44. The outer wall 46is disposed at the periphery of the cover portion 44. The inner wall 46is spaced slightly inward from the outer wall 44 and is concentric withthe outer wall 46. The walls 46 and 48, along with the previouslymentioned seal cavity 34, forms a labyrinth seal.

The spring 60 is disposed around the hub 42 of the bearing shield 40.One end of the spring 60 presses against the bearing 38 while theopposite end presses against the bearing shield 40. Thus, the spring 36biases the stub shaft 50 to an extended position.

To install the roller 10 between parallel fame members 12, the roller 10is held in a tilted position while the stub shaft 50 at one end isinserted into its mating mounting hole 14. After the first end of theroller is inserted into the mounting hole 14, the stub shaft 50 on theopposing end is pressed inward to move the stub shaft 50 to a retractedposition (see FIG. 2). The second end is then lowered between the framemembers 12 until the stub shaft 50 is aligned with its mating mountinghole 14 in the frame member 12. When the stub shaft 50 is aligned withthe mounting hole 14, the spring 36 urges the stub shaft 50 to anextended position so that it engages the mounting hole 14 (see FIG. 3).The bolt 62 is then inserted through the mounting hole 14 in the framemember 12 and threaded into the threaded hole 58 in the stub shaft 50 tosecure the roller 10 in place.

FIGS. 4-6 illustrate an alternate embodiment of the roller 10. Thisembodiment uses the same roller 10 and bearing housing 22 as previouslydescribed. The description of these elements, therefore, will not berepeated. However, it should be noted that the reference numbers inFIGS. 4-6 which are the same as the reference numbers in FIGS. 1-3indicate the same parts.

The second embodiment, shown in FIGS. 4-6, eliminates the stub shaft 50.Instead, a bearing shaft 70 is integrally formed with the bearing shield40. The bearing shaft 70 isjournalled in the bearing 38. The bearingshaft 70 is hollow and internally threaded. The inner end 72 of thebearing shaft is designed to retain the bearing shaft 70 in place. Twodiametrically opposed relief slots 74 are formed in the inner end 72 ofthe bearing shaft 70. The purpose of the relief slots 74 is tofacilitate insertion of the bearing shaft 70 through the bearing 38.When the bearing shaft 70 is pressed into the bearing 38, the inner end72 collapses inwardly to allow the bearing shaft 70 to pass through thebearing 38. When the bearing shaft 70 passes through the bearing 38, theinner end 72 expands back to its original form due to the inherentresiliency of the material.

An insert 80 is adapted to fit into a recess formed in the outer surfaceof the bearing shield 40. The insert 80 includes a hexagonal stub member82 and a base portion 84. The hexagonal stub member 82 mates with thehole 14 in the frame member 12. The base portion 84 of the insert 80fits into a recess or socket formed in the outer surface of the bearingshield 40. The base 84 of the insert 80 and the recess both have asquare configuration to prevent rotation of the insert 80 relative tothe bearing shield 40.

A hole 86 extends through the insert 80. The bolt 62, which secures theroller 10 to the frame member 12, passes through the insert 80 andengages the threads on the inner surface of the bearing shaft 70.Consequently, the insert 80 gets captured between the bearing shield 40and the frame member 12 so that it cannot be dislodged.

One advantage of using insert 80 is that it can be easily interchangedin the field. For example, if the frame member 12 has square mountingholes 14 rather than hexagonal mounting holes 14, an insert 80 with asquare stub 82 can be inserted into the shield 40. Without thereplaceable insert 80, it would be considerably more difficult to modifythe roller to fit a square mounting hole 14.

Based on the foregoing, it will be apparent that the conveyor roller 10of the present invention can be easily installed and removed from apre-fabricated conveyor frame. Moreover, the present invention employs a“shaftless” design which substantially reduces the weight of the roller.

The present invention may, of course, be carried out in other specificways than those herein set forth without departing from the spirit andessential characteristics of the invention. The present embodiments are,therefore, to be considered in all respects as illustrative and notrestrictive, and all changes coming within the meaning and equivalencyrange of the appended claims are intended to be embraced therein.

What is claimed is:
 1. A roller insert for a conveyor roller tube, saidroller insert comprising: a) a generally cylindrical housing; b) abearing mounted within said cylindrical housing, said bearing having aninner race and an outer race; c) a stub shaft positioned within saidbearing and movable between extended and retracted positions, said stubshaft having a stop to limit the positioning of said stub shaft in saidextended position, said stop contacting said inner race of said bearing;d) a bearing shield disposed around said stub shaft; and e) a biasingdevice to bias said stub shaft to said extended position.
 2. The insertof claim 1, wherein said stub shaft has a hexagonal outer shape.
 3. Theinsert of claim 1, wherein said bearing housing includes an innercylindrical wall frictionally engaging said bearing, and an outercylindrical wall engaging the roller tube. 4.The insert of claim 1,wherein said cylindrical housing is rotatable relative to said stubshaft.
 5. The insert of claim 1, further including a lip extendingoutward from said cylindrical housing for positioning the roller insertwithin the roller tube.
 6. The insert of claim 1, wherein said biasingdevice is positioned between said bearing and said bearing shield.
 7. Aroller insert for a roller tube comprising: a) a housing having asubstantially cylindrical outer wall and an inner wall; b) a bearingpositioned against said inner wall of said housing said bearing havingan inner race and an outer race; c) a stub shaft positioned within saidbearing and being movable between extended and retracted positions; d) abiasing device positioned about said stub shaft to bias said shafttowards said extended position; and e) a stop to limit the axialmovement of said stub shaft in said extended position said stopcontacting said inner race of said bearing.
 8. The insert of claim 7,wherein said stub shaft extends outward from a first end of said housingin said extended position.
 9. The insert of claim 8, wherein said stubshaft first end is substantially aligned with said first end of saidhousing in said retracted position.
 10. The insert of claim 7, furtherincluding a bearing shield substantially positioned along a first end ofsaid housing, said bearing shield having an aperture through which saidstub shaft extends.
 11. The insert of claim 10, wherein said stopcontacts said bearing to limit movement of said stub shaft in saidextended position.